1. Field of the Invention
The present invention relates to a liquid discharge head and a liquid discharge apparatus, which are used for a printer and a video printer as an output terminal of a copying machine, a facsimile, a word processor, a host computer, or the like and a method of manufacturing the liquid discharge head. Particularly, the present invention relates to the liquid discharge head having a device substrate, in which an electrothermal device is formed to generate thermal energy used for discharge of a liquid, a liquid discharge and recording apparatus on which the liquid discharge head is mounted, and the method of manufacturing the liquid discharge head. In other words, it relates to the liquid discharge head, which is used for recording by discharging a recording liquid such as ink from a discharge port as a flying droplet to attach the liquid to a recording medium, and the method of manufacture thereof.
2. Related Background Art
Ink jet recording method, i.e., so-called bubble jet recording method, in which energy such as heat is applied to ink to cause a status change of ink accompanied by an abrupt volume change, ink is discharged from the discharge port by an action force based on the status change of ink, and this is attached to a recording medium to form an image, has been conventionally known. In the recording apparatus using this bubble jet recording method, as disclosed in U.S. Pat. No. 4,723,139 specification, the discharge port to discharge ink, an ink path to communicate with this discharge port, and the electrothermal conversion body as energy generating means to discharge ink are generally arranged.
According to such a recording method, a high quality image can be recorded in a high speed and low noise and the discharge port for discharge of ink can be arranged in a high density in the head employing this recording method and therefore, there are many excellent advantages: a recorded image of high resolution and a color image can be readily yielded by a small apparatus. Thus, in recent years, this bubble jet recording method is used for many office appliances such as printer, copying machine, facsimile, or the like, and also used for such industrial systems as printing apparatus.
According to increasing application of such bubble jet technology to a product of many aspects, the following various requirements are recently increasing.
For example, a measure for the requirement of improving energy efficiency is exemplified by optimization of a heating element through adjustment of a thickness of a protecting film of the heating element. This measure expresses an effect to improve a conduction efficiency of heat generated to a liquid.
Furthermore, in order to yield the high quality image, a driving condition was proposed to provide the liquid discharge method capable of good ink discharge based on a fast speed of ink discharge and stable bubble occurrence and also in consideration of high speed recording, in order to obtain the liquid discharge head by which the discharged liquid is rapidly refilled in a liquid flow path, one, of which shape of the liquid flow path has been improved, has been proposed.
In addition, in reconsideration of a principle of liquid discharge, studies were carried out to provide a new liquid discharge method, not realized conventionally, employing a bubble and a head used therefor and there have been proposed the liquid discharge method and the head used therefor disclosed in Japanese Patent Application Laid-Open No. 9-201966.
Hereby, the conventional liquid discharge method and the head used therefor disclosed in Japanese Patent Application Laid-Open No. 9-201966 will be described below with reference to FIGS. 14A to 14D, FIG. 15 and FIG. 16. FIGS. 14A to 14D are figures to explain the discharge principle of the conventional liquid discharge head and each of FIG. 14A to FIG. 14D is a sectional view along with a direction of the liquid flow path. FIG. 15 is a partially broken-away perspective view of the liquid discharge head shown in FIGS. 14A to 14D, FIG. 16 is the sectional view of a modified example of the liquid discharge head shown in FIGS. 14A to 14D. The liquid discharge head shown in FIGS. 14A to 14D and 16 is one configured most basically to improve a discharge force and discharge efficiency by controlling a direction of travelling of the pressure and the direction of a bubble growth on the basis of the bubble in discharging the liquid.
xe2x80x9cUpstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d used in the following description are expressions for the direction of the liquid flow from a source of supplying the liquid toward the discharge port through a top of the region, where the bubble occurs, or the direction of this configuration.
xe2x80x9cDownstream sidexe2x80x9d related to the bubble itself represents mainly the discharge port of the bubble, which is regarded as works directly on discharge of the droplet. More specifically, to a center of the bubble, it means the downstream side in the flow direction as above described and the direction of the above configuration or the bobble generated in the region of the downstream side of the center of the area of the heating element. (Similarly, the xe2x80x9cupstream sidexe2x80x9d of the bubble itself means, to the center of the bubble, the upstream side of the direction in the flow direction as described above and the direction of the above described configuration or the bubble generated in the region of the upstream side of the center of the area of the heating element.)
In addition, xe2x80x9ccomb shapexe2x80x9d means a shape in which a fulcrum part of a movable member is a common member and a distal end of a free end of the movable member is opened.
In the liquid discharge head shown in FIGS. 14A to 14D, a device substrate 501 is one prepared by forming a silicon oxide film or a silicon nitride film with a purpose of insulation and heat reserving on the substrate made of silicon or the like and thereupon, an electric resistor layer and wire is patterned to constitute the heating element 502. This wire applies a voltage to the electric resistor layer and applies a current to the electric resistor layer to heat the heating element 502.
A ceiling board 511 is one to comprise a plurality of the liquid flow path 503 corresponding to all heating elements 502 and a common liquid chamber 505 for supply of the liquid to all liquid flow paths 503 and a flow path side wall is integrally installed to extend from a ceiling part to all heating elements 502. On the other hand, On the ceiling board 511, a plurality of the discharge ports 504 are formed to communicate with all liquid flow paths 503 with outside.
The ceiling board 511 can be formed by depositing a material such as silicon nitride, silicon oxide, or the like, that are used for a side wall of the liquid flow path 503, on the silicon substrate by a publicly known film forming method such as the CVD, etching a part of the liquid flow path 503 and then, adhering the ceiling part.
On the part, corresponding to the liquid flow path 503, of the device substrate 501, a plate-like movable member 506 facing the heating element 502 is installed like a cantilever and the one end of the upstream side of the movable member 506 is fixed to a base 507. The movable member 506 is supported by the base 507 to possess the fulcrum 508 in a displacing occasion. On the other hand, the movable member 506 is formed in comb shape by patterning the deposited film in a stage to form the liquid flow path 503 and the side wall thereof as described above by a publicly known film forming method and consists of such silicon-based material as silicon nitride, silicon oxide, or the like.
The movable member 506 has the fulcrum 508 in the upstream side of a large flow flowing from the common liquid chamber 505 to the discharge port 504 side by a discharging action of the liquid through the top of the movable member 506 and is arranged with a distance of 15 xcexcm from the heating element 502 to have the free end 509 in the downstream side toward this fulcrum 508 and in a state to cover the heating element 502 in a position facing the heating element 502. The region between this heating element 502 and the movable member 506 becomes a bubble generating region 510.
Next, the action of the liquid discharge head configured as described above will be described with reference to FIG. 14A to FIG. 14D.
First, in FIG. 14A, ink is filled in the bubble generating region 510 and the liquid flow path 503.
Next, in FIG. 14B, heating the heating element 502 allows heat to work on the liquid of the bubble generating region 510 between the heating element 502 and the movable member 506 to generate the bubble 511 in the liquid on the basis of a film boiling phenomenon described in U.S. Pat. No. 4,723,129 specification or the like. Actions of the pressure created by occurrence of the bubble 511 and the bubble 511 on the movable member 506 are assigned higher priority. The movable member 506, as shown in FIG. 14B, FIG. 14C, or FIG. 15, is displaced to open largely to the discharge port 504 side around the fulcrum 508. In accordance with displacement or the state of displacement of the movable member 506, because of travelling of the pressure based on occurrence of the bubble 511 and the distal end of the bubble 511 having a width, a bubbling power of the bubble 511 can be easily led to the discharge port 504 side and hence, the discharge efficiency, discharge force, and discharge speed of the droplet and can be radically improved. For reference, a reference character C in the figure indicates the center of the area of the heating element.
As described above, the art described in Japanese Patent Application Laid-Open No. 9-201966 or the like is the art to control actively the bubble by making a relation of a position of the fulcrum and the free end of the movable member in the liquid flow path to the relation the free end of the movable member is located in the discharge port side, i.e., the downstream side and the movable member is arranged facing the heating element or the bubble generating region.
Each configuration of the device substrate 601 of the liquid discharge head, heating element 602, liquid flow path 603, discharge port 604, common liquid chamber 605, and bubble generating region 609, that are shown in FIG. 16, are same as those of the liquid discharge head described based on FIGS. 14A to 14D and thus, detailed description of the configurations thereof will be omitted.
In the liquid discharge head shown in FIG. 16, on the one end of the movable member 606 formed like the cantilever, a step part 606a is made and to the device substrate 601, the movable member 606 is directly fixed. By this, the movable member 606 is held on the device substrate 601, the fulcrum 607 of the movable member 606 is established, and the free end 608 is made in the downstream side toward this fulcrum 607.
As described above, through installing the base on a fixed part of the movable member or installing the step on the fixed part of the movable member, a gap ranging from 1 to 20 xcexcm is formed between the movable member and the heating part and an effect to improve a liquid discharge efficiency is fully expressed by the movable member. Consequently, according to the liquid discharge head based on the discharge principle described above, a synergistic effect of the bubble generated and the movable member displaced thereby can be yielded and the liquid around the discharge port can be efficiently discharged. Therefore, in comparison with the discharge method and the liquid discharge head of the conventional bubble jet system lacking the movable member, liquid discharge efficiency is improved.
In the liquid discharge head having the movable member as described above, the movable member is displaced according to a change of the pressure of the bubble and in displacement, a stress according to the displacement is added to the movable member. This stress works particularly largely on the movable member around a base (fulcrum) of the movable member to influence durability of the movable member.
However, as described above, in the liquid discharge head having the plate-like movable member, the material of the movable member is SiN and ceramic and hence, when there is s defect such as a crack and a burr in a edge of a side part thereof, durability of the movable member is occasionally distinctly reduced. For example, when the edge, particularly of the side part the upstream of the heating element, of the movable member has not been chamfered but the edge is made in a right-angled shape, the stress concentration occurs in the edge in displacement of the movable member. In addition, the deposition film is formed on the substrate and the deposition film is patterned to form the movable member and thus, a pin hole and the crack may occur in the edge of the side part of the movable member.
In addition, the movable member is formed on the substrate by film forming method and hence, shape of the movable member is influenced by the surface condition of a bottom layer on which the material layer of the movable member is formed. As a result, as described above, the shape of the edge of the side part of the movable member becomes occasionally in the shape easy to concentrate the stress in displacement of the movable member.
Consequently, in the case where a very large bubble occurs in the bubble generating region and the movable member is displaced in a very large degree, the movable member breaks at the base of the movable member. This is a problem.
An object of the present invention is to eliminate the part with an abruptly changed-shape of the movable member and make a structure possible to relax stress concentration by constituting the movable member with the film with an equal quality to improve durability of the movable member and provide the liquid discharge head and the liquid discharge apparatus, that are stable in discharge characteristic and of high reliability, and the method of manufacturing the liquid discharge head having such performances.
In order to attain the above described objects, according to the present invention, a liquid discharge head includes: a discharge port to discharge a liquid; a liquid flow path communicating with the above described discharge port and having a bubble generating region to let the liquid generate a bubble; a discharge energy generating device, installed in a substrate, to generate thermal energy to let the liquid generate the bubble in the above described bubble generating region; and a plate-like movable member located in an position opposite to the above described discharge energy generating device with a distance from the above described discharge energy generating device, fixed an end part of an upstream side thereof in a direction of a flow of the liquid in the above described liquid flow path and made the end of a downstream thereof free, and formed on the above described substrate by film formation, wherein the side part of the above described movable member has no right angle or no acute angle.
Also according to the present invention, wherein an edge of the side part of the above described movable member has a curved face.
Further, according to the invention, the liquid discharge head includes: the discharge port to discharge the liquid; the liquid flow path communicating with the above described discharge port and having the bubble generating region to let the liquid generate the bubble; the discharge energy generating device, installed in the substrate, to generate thermal energy to let the liquid generate the bubble in the above described bubble generating region; and the plate-like movable member located in the position opposite to the above described discharge energy generating device with the distance from the above described discharge energy generating device, fixed the end part of the upstream side thereof in the direction of the flow of the liquid in the above described liquid flow path and made the end of the downstream thereof free, and formed on the above described substrate by film formation, wherein an edge of the side part of said movable member is chamfered.
It is preferable that the above described movable member is one formed by photolithographic technique on a device substrate on which the above described discharge energy generating device is installed.
Also according to the present invention, the liquid discharge head having: the discharge port to discharge the liquid; the liquid flow path communicating with the above described discharge port and having the bubble generating region to let the liquid generate the bubble; the discharge energy generating device, installed in the substrate, to generate thermal energy to let the liquid generate the bubble in the above described bubble generating region; and the plate-like movable member located in the position opposite to the above described discharge energy generating device with the distance from the above described discharge energy generating device, fixed the end part of the upstream side thereof in the direction of the flow of the liquid in the above described liquid flow path and made the end of the downstream thereof free, and formed on the above described substrate by film formation, wherein on a surface of the above described substrate, there are formed a plurality of electrode layers, that is extended to at least a part of a region and a part around the region corresponding to a plurality of the above described movable member and is electrically connected to the above described discharge energy generating device; and in comparison with a width in a direction perpendicular to the direction of a liquid flow in the above described liquid flow path in all of the above described electrode layers, the width in the direction right-angled to the direction of a liquid flow in the above described liquid flow path and in parallel to a surface of the above described device substrate in the above described movable member becomes smaller.
It is preferable that a constituting material of the above described movable member is a ceramic.
Also it is preferable that the constituting material of the above described movable member is silicon nitride.
In the invention described above, the side part of the plate-like movable member, facing the discharge energy generating device keeping the distance from the device, formed by film formation has no right-angled or acute-angled part and the edge of the side part is curved or the edge is chamfered and thus, in discharging the liquid from the discharge port by displacing the movable member by letting the liquid to generate the bubble by the discharge energy generating device in the bubble generating region of the liquid flow path and in extreme displacement of the movable member, stress concentration is relaxed in the side part of the movable member. Therefore, the liquid discharge head as described above has no acutely changed part in the shape of the side part of the movable member and hence, the stress according to displacement thereof is applied to the movable member in displacement of the movable member, it is prevented to cause cracks of the movable member and fracture of the movable member. For example, the following structure is realized: in the case where the movable member is formed by photolithographic technique, the movable member is constituted by the film of the equal quality to allow stress concentration to relax. As a result, durability of the movable member is improved and discharge characteristics become stable and thus, the liquid discharge head of high reliability is realized.
Further, the liquid discharge apparatus has the above described liquid discharge head and actuation signal supply means for supplying an actuation signal for discharge of the liquid from the liquid discharge head.
Further, the liquid discharge apparatus according to the present invention has the above described liquid discharge head and recording-medium carrying means for carrying a recording medium to receive the liquid discharged from the liquid discharge head.
Further, the above described liquid discharge apparatus carries out recording through discharging an ink from the above described liquid discharge head and attaching the above described ink to the recording medium.
Furthermore, according to the present invention, a method of manufacturing the liquid discharge head includes: a device substrate, a plurality of discharge energy generating devices to generate thermal energy to let the liquid generate a bubble, being provided in parallel on a surface thereof; a plurality of the liquid flow paths, in which wXH of the above described discharge energy generating devices is arranged, having a bubble generating region to let the liquid generate a bubble; a plurality of discharge ports to discharge the liquid in the liquid flow path, each of the discharge ports communicating with each of the above described liquid flow paths; a flow path wall member mounted on the above described device substrate to form a plurality of the above described liquid flow paths; and a plurality of plate-like movable members, which are mounted on the above described device substrate to face each of said plurality of the above described discharge energy generating devices with an interval with respect to each of the above described discharge energy generating devices and an end part of an upstream side in the direction of the liquid flow in the above described liquid flow path is fixed and a downstream end is a free end, wherein the method of manufacturing the liquid discharge head, has a post-treatment step of removing a right-angled part projecting to make a distal end right-angled in an edge part of a side part of the above described movable member and an acute-angled part projecting to make the distal end acute-angled in the edge after a plurality of the above described movable members is formed on the above described device substrate by photolithographic technique.
Furthermore, it is preferable that in the above described post-treatment step, the edge of the side part of the above described movable member is processed to make the edge to curved one and the edge of the side part of the above described movable member is processed to make the edge to chamfered one.
Also it is preferable that the above described post-treatment step is the process to soak the above described movable member in a etching solution and the step of processing the above described edge by radiating a laser light on the edge of the edge of the side part of the above described movable member.
Also according to the present invention, the method of manufacturing the liquid discharge head includes: a device substrate, a plurality of discharge energy generating devices to generate thermal energy to let the liquid generate the bubble, being provided in parallel on a surface thereof; a plurality of liquid flow paths, in each of which each of the above described discharge energy generating devices is arranged, having the bubble generating region to let the liquid generate the bubble; a plurality of discharge ports to discharge the liquid in the liquid flow path, each of discharge ports communicating with each of the above described liquid flow paths; a flow path wall mounted on the above described device substrate to form a plurality of liquid flow paths; and a plurality of the plate-like movable members, which are mounted on the above described device substrate to face each of a plurality of the above described discharge energy generating devices with an interval with respect to each of the above described discharge energy generating devices and an end part of an upstream side in the direction of the liquid flow in the above described liquid flow path is fixed and the downstream end is the free end; a ceiling board, that is adhered to a face of a side opposite to the above described device substrate side, of a plurality of the above described side wall of the flow path; on the surface of the above described device substrate, a plurality of electrode layers, extended to at least the part of the region and the part around the region corresponding to a plurality of movable members and each of which is electrically connected to the above described discharge energy generating device, are formed; wherein the method of manufacturing the liquid discharge head comprises the steps of: preparing the above described device substrate in which a plurality of discharge energy generating devices are mounted on the surface of the above described device substrate and a plurality of electrode layers; forming a pattern member, corresponding to a space of the above described bubble generating region, on the surface of the above described device substrate; layering a first material layer for forming the above described movable member to cover the above described pattern member; layering an etching-resistant protection film, having etching-resistant property against the above described first material layer, on the surface of the above described first material layer; patterning the above described etching-resistant protection film to make the above described movable member of which angle is right-angled to the direction of the liquid flow in the above described liquid flow path and width is small in a shape in parallel to the surface of the above described device substrate in the above described movable member; layering a second material layer for forming the above described side wall of the flow path to cover the above described etching-resistant protection film patterned; removing the part, corresponding to the above described liquid flow path, of the above described second material layer by etching and forming the above described side wall of the flow path and the above described liquid flow path; and removing the above described pattern member after the step for forming the above described liquid flow path and forming the above described movable member.
Using silicon nitride as the material of the above described movable member is preferable.
Also according to the method of manufacturing the above described liquid discharge head, it is preferable to use silicon nitride as the material of the above described movable member, PSG as the material of the above described pattern member, aluminum as the material of the above described etching-resistant protection film.
According to the method of manufacturing the above described liquid discharge head, after a plurality of the plate-like movable members are formed on the device substrate, on which a plurality of the discharge energy generating devices are mounted, by photolithographic technique, the right-angled part and the acute-angled part projecting from the edge part of the side part of the movable member are removed to make the edge to a curved face and to make the edge chamfered and thus, the following structure is realized: the acutely changed part is removed from the shape of the edge of the side part of the movable member and the movable member is constituted by the film of equal quality and hence, the stress concentration is relaxed. In this liquid discharge head, in displacing the movable member by the discharging action of the liquid and in extreme displacement of the movable member, stress concentration is relaxed in the edge of the side part of the movable member. Therefore, even if stress according to displacement of the movable member is applied to the movable member, it is prevented to cause cracks of the movable member and fracture of the movable member. As a result, durability of the movable member is improved and discharge characteristics become stable and thus, the liquid discharge head of high reliability is realized.